1. Field of the Invention
The present invention is directed to a door closer which provides even pressure to a door throughout the range of the door swing.
2. Description of Related Art
In the door closer/operator industry today there is the need for the user to feel a constant force when opening the door, especially on doors needing to meet ADA requirements. According to the prior art, one solution is a double lever arm which changes the vector angle between the arm and the door as the torque increases on the door closer/operator due to a linear spring. Another solution is the cam and roller design where the cam profile changes with the spring compression to provide a constant torque output. Prior art door closers include those of U.S. Pat. No. 4,653,227; U.S. Patent Publication No. 2013/0081227; U.S. Pat. No. 4,763,385; and U.S. Pat. No. 8,732,904. Each of these designs has disadvantages. Each has mechanical losses due to friction, the rack and pinion setup on the double lever arm closers and the cam roller on the cam/roller design. Additionally, they each require very strict tolerances for proper functionality.